This invention generally relates to slider-operated flexible zippers for use in reclosable pouches, bags or other packages of the type in which material, such as foodstuff, detergent, etc., may be stored.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies often include a plastic zipper and a slider. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure members, etc.
Conventional slider-operated zipper assemblies typically comprise a plastic zipper having two interlocking profiles and a slider for opening and closing the zipper. In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger at one end that is inserted between the profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction. Other types of slider-operated zipper assemblies avoid the use of a separating finger. For example, U.S. Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually interlockable profiled structures, portions of which form a fulcrum about which the profiled structures may be pivoted out of engagement when lower edges of the bases are forced towards each other by the moving slider.
Reclosable bags are finding ever-growing acceptance as primary packaging, particularly as packaging for foodstuffs such as cereal, fresh vegetables, snacks and the like. Such bags provide the consumer with the ability to readily store, in a closed, if not sealed, package any unused portion of the packaged product even after the package is initially opened. To gain acceptance as a primary package for foodstuffs, it is virtually mandatory that the package exhibit some form of tamper evidence to protect the consumer and maintain the wholesomeness of the contained product. In addition, in many cases it is necessary that food product be hermetically packaged. This may readily be accomplished by forming a plastic bag of a film having the appropriate barrier properties. However, where the bag is provided with a zipper, a problem arises in properly sealing the bag at the opening to be closed by the zipper, since the zipper itself does not provide a hermetic seal. The presence of a slider on a zipper poses an additional impediment to hermetic sealing of the package since even in the fully closed park position, the opening end of the slider typically causes the zipper closure members to separate.
One solution to the problem off providing both tamper evidence and hermetic sealing is to manufacture packages wherein the slider-zipper assembly is enclosed by a header. Before anyone can open the zipper and tamper with the contents of the package, the header must be torn at least partly, leaving evidence to dissuade any consumer from buying that package. Also, since the header is contiguous with the bag body, the fully enclosed zipper does not interfere with hermetic sealing of the package.
Many existing form-fill-seal (FFS) machines operate on bag making film and do not incorporate equipment for attaching zipper assemblies to the bag making film. However, zipper application machines are available that can be coupled to the FFS machine to provide the zipper application function. In addition, a slider insertion device may be incorporated as part of the zipper application station. However, operators of FFS machines who do not wish to purchase a zipper applicator and a slider inserter require that bag making film with slider-zipper assemblies be available for purchase. This film can then be run through the FFS machine. Although the packager may need to modify his FFS machine to handle bag making film with slider-zipper assemblies attached, including providing clearance for the sliders to pass through the machine, the major capital investment of a zipper application system can be avoided.
There is a need for a reclosable package design whereby bag making film with preattached slider-zipper assemblies can be formed, filled and sealed without the FFS machine needing to perform any zipper application step.